Since B. Rosenberg et al. discovered in 1969 the fact that cis-dichlorodiammineplatinum(II), a platinum complex called cisplatin by generic name, has anticancer activity against Sarcoma 180, intensive research and development works have hitherto been conducted on cancer chemotherapy using platinum complexes in various countries and now platinum complexes as unique broad-spectrum anticancer agents are attracting much attention. Reportedly, however, cisplatin has very strong nephrotoxicity and, due to its accumulability, causes gastrointestinal disorders, hypofunction of the bonemarrow, hearing impairment and so forth and, furthermore, causes severe nausea and vomiting, among others, at the time of administration, causing unimaginably severe pain in patients. In addition, the solubility of cisplatin in water is as low as about 1 mg/ml and therefore it is difficult to formulate therapeutically effective dosage forms containing it. In spite of these drawbacks, cisplatin is currently in use as an essential means in the treatment of testicular tumor, ovarian cancer, bladder cancer, head and neck tumors, etc., but its use is much restricted as a matter of course. On the other hand, those cis-dichloroplatinum(II) complexes that are known to have anticancer activity, such as cis-dichloro(1,2-diaminocyclohexane)platinum(II), cis-dichloro(2-aminomethylpyridine)platinum(II) and cis-dichlorobis(cyclopentylamine)platinum(II), are still less water-soluble than cisplatin. Accordingly, a number of investigations have been conducted in various countries to find out platinum complex anticancer agents free from such drawbacks of cis-dichloroplatinum(II) complexes and, as a result, there have been developed, for example, 1,1-cyclobutanedicarboxylatodiammineplatinum(II) (carboplatin by generic name), cis-dichloro-transdihydroxobis(isopropylamine)platinum(IV), R-1,1-cyclobutanedicarboxylato(2-aminomethylpyrrolidine)platinum(II), (glycolato-O,O')-diammineplatinum(II), 1,1-cyclobutanedicarboxylato( 2-methyl-1,4-butanediamine)platinum(II) and oxalato(1R,2R-cyclohexanediamine)platinum(II).
It has also been reported that compositions containing coupling products between organic macromolecules having a molecular weight of 5,000-60,000, such as polyamino acids and anionic polysaccharides, and platinum or palladium complexes are suited for use in the treatment of tumors and for the treatment and prevention of trypanosomiasis (cf. Japanese Kokai Tokkyo Koho No. 59-116221).
The platinum complexes mentioned above can hardly be said to be satisfactory with respect to reduction in side-effects, indications and water-solubility, among others. For the reasons mentioned above, it is difficult to expect that some novel anticancer agent free from various drawbacks as mentioned above would be born from among low-molecular platinum complexes.
The above-mentioned compositions can hardly be said to be satisfactory in terms of anticancer activity, toxicity and/or solubility in water.
Accordingly, it is an object of the invention to provide a novel water-soluble compound which shows side-effects to a less extent, is broader in anticancer spectrum and has better anticancer activity as compared with the conventional platinum complex anticancer agents.
Another object of the invention is to provide a process for producing said novel compound.
A further object of the invention is to provide a pharmaceutical composition containing said novel compound as well as a method of treating cancer which comprises administering said novel compound.